Electrodeposition of copper and copper alloys



United States Patent 3,111,465 ELECTRODEPOSITION OF COPPER AND COPPER ALLOY Frank Passal, Detroit, Mich, assignor, by mesne assignments, to M & T Chemicals Inc., New York, N.Y., a

corporation of Delaware N0 Drawing. Filed Feb. 9, 1959, Ser. No. 791,824 17 Claims. (Cl. 204-44) The present invention relates to the electrodeposition of decorative and protective copper and copper alloys from improved alkaline-cyanide type baths. The present application is a continuation-in-part application of US. Serial No. 666,766 and No. 666,784, both filed June 19, 1957, issued as U.S. Patent Nos. 2,873,234 and 2,873,235, respectively.

The object of this invention is to provide improved baths for the electrodeposition of copper and copper alloys.

Another object of this invention is to provide an improved process for electrodepositing copper and copper alloys.

The present invention contemplates electrodepositing decorative and/or protective copper or copper alloys from alkaline-cyanide baths containing between 0.01 and 0.2 g./l. (grams per liter) of N-substituted fl-alanines selected from the class of compounds having the following two general structural formulae:

wherein R is an alkyl radical having from 8 to about 16 carbon atoms in the chain; R is a group selected from hydrogen and alkyl radicals having 1 to 4 carbon atoms (preferably hydrogen); and X is a cation selected from the class consisting of hydrogen, sodium, potassium, calcium, lithium, magnesium and ammonium ions (preferably sodium :or potassium). The alkyl radicals (R) are generally derived from long chain natural alcohols, the preferred natural product being the coconut derivative, generally called coco, which is predominantly a C natural product. The alkyl radicms having between 12 and 14 carbon atoms in the chain are preferred. These ,B-alanines are usually available in the form of the sodium or the potassium salts which are preferred compounds for use in the present invention. The salts of the other cations noted hereinbefore are also useful, as are the free acids where care is taken to vent HCN evolved. The amino type material, Formula No. 1 hereinbefore, is preferred to the imino type material, Formula No. 2 hereinbefore. This preference is based on its somewhat more advantageous solubility and adsorption characteristics. Although baths may contain these B-alanines in amounts between 0.01 to 0.2 g./l. it is preferred to use amounts between 0:04 and 0.09 g./l.

The preferred B-alanines of this invention have the following general structure: RNHCH -CH -COONa (an alkyl B-amino propionate), and RN(CH CH COONa) (an alkyl B-imino dipropionate). They are stable in the electrolyte and even impart some brightening action. A compound of this class which has been successfully used is the sodium salt of a coconut alcohol derivative of B-amino propionate.

The N-substituted S-alanines are useful in a wide variety of cyanide type baths containing excess potassium or sodium cyanide (herein called free cyanide) and 'ice processes for the plating of copper and copper alloys. These generally include the following:

( 1) Copper strike baths:

Copper About 15 g./l. Free potassium or sodium cyanide 11-15 g./l. Temperature 48-60 C. Agitation Little or none. Current density 10-50 a.s.f. (2) Intermediate speed baths:

Copper 30-38 g./l. Free potassium or sodium cyanide 7.5-15 g./l. Potassium or sodium hydroxide 15-30 g./l. Potassium or sodium carbonate (optional) About 15 g./l. Temperature Generally -82 C. Agitation Yes. Current density 10-80 a.s.f. (3) Bright copper baths:

Copper 37-75 g./l. Free potassium or sodium cyanide 3.7-15 g./l. Potassium or sodium hydroxide 15-30g./l. Brightener, e.g., selenium bis diethyldithiocarbamatm About 0.004 g./l. Temperature Generally 65-82 C. Agitation Yes. Current density 5-50 a.s.f. (4) Brass plating baths:

CuCN 30-225 g./l. Zn(CN) 9.4-71g./1. Total NaCN 56-425 g./l. Na CO 30-123 g./l. Free NaCN 30-225 g./l. Temperature 20-38 C. Current density 12-20 a.s.f. (5) Bronze plating baths:

Tin (as stannate) 11-16 g./1. Copper 18-30 g./l. Free KCN or NaCN 20-25 g./l. Free KOH or NaOH 610.6 g./l. Temperature 62-71 C. Current density 20-100 a.s.f.

These baths and operating conditions are merely illustrative of plating from alkaline-cyanide type copper and copper alloy baths. Alkaline-cyanide baths and processes are described in Modern Electroplating, edited by A. G. Gray, pages 98-114 and 194-225 (1953). Electroplating from the bronze and brass plating baths illustrated may utilize the respective alloy anodes or copprimary function is as an anti-pitting agent. They also tend to make the bath more tolerant to impurities.

As is generally known in electrodeposition from alkaline-cyanide baths best results are usually achieved when the process utilizes a method of preventing the thin film immediately adjacent the cathode from becoming depleted in metal ion content. This is conventionally accomplished by agitation such as solution pumping, cathode movement, air agitation, or by diffusion efiects, e.g., current interruption, periodic reversal, etc., or, by combinations thereof. The use of air agitation is generally not preferred in baths containing the N-substituted fi-alanines. Their action on the bath is such that the bath is characterized by a relatively stable foam. When air agitation is used the foam blanket is likely to grow to high. However, under particular conditions this might be acceptable although generally it is preferred to use one of the other methods, e.g., cathode movement or solution pumping, to achieve the results desired.

For the purpose of providing a better understanding of this invention, examples of various baths and process conditions are summarized in Tables I and II; Table I illustrating copper plating, and Table II illustrating bronze plating.

brighteners (in conjunction with metallic brighteners) in bronze plating.

The sound copper and copper alloy electrodeposits obtained from alkaline-cyanide type baths of the present invention are obtained on such conventional basis metals as iron, steel, nickel, zinc, lead, copper, etc., and alloys thereof. On certain basis metals such as iron or steel and zinc-base die castings the basis metal is first given an initial thin flash of copper from a lowefficiency cyanide copper bath.

As many embodiments of this invention may be made without departing from the spirit and scope thereof, it is to be understood that the invention includes all such modifications and variations as come within the scope of the appended claims.

I claim:

1. An improved alkaline-cyanide bath for plating a metal selected from the class consisting of copper and copper base alloys which comprises .copper cyanide, free cyanide, and between 0.01 g./l. and 0.2 g./l. of at least Table I Constituent in g./l. or Plating Condition 1 2 3 4 5 Ouprous cyanide 60 75 75 Potassium cyanide (to Sodium cyanide (total) Potassium hydroxide. Sodium hydroxide,"

Free potassium cyanide- Free sodium cyanide- Potassium sodium tartrate Potassium gluconate Potassium saecharate Selenium diethyldithio-carbamate.

Tellurium diethyldithio-carbamate Lead in g./1. added as Pb(CzH3Oz)2-3H2O 0. 002 Potassium thioeyanate 5 TEA N-lauryl B-amino pr0piot1ate Sodium N coco B-amino propionate Sodium N-lauryl ti-amino propionate-. Disodium N-lauryl fl-imino dipropionate Disodium N-tallow B-imino dipropionate Sodium N-lauryl til-amino butyrate Temperature C 1 The abbreviation TEA refers to the triethanolammonium radical.

Table II Constituent in g. /l. or Plating Condition 1 2 3 4 The cyanide alkaline type of baths for electrodeposition of copper and copper alloys which have incorporated therein the N-substituted ,B-alanines are particularly free rinsing. Parts taken from these baths are often so free of salts and other surface material that it is not necessary to clean them before nickel plating. These fi-alanines are exceedingly stable in cyanide baths. If there is decomposition, the products do not produce any adverse effects on the cathodic deposit and are compatible with the bath. 75

one B-alanine selected from the class consisting of compounds having the following formulae:

wherein R is an alkyl radical having from 8 to 16 carbon atoms in the chain, R is a group selected from the class consisting of hydrogen and alkyl radicals having 1 to 4 carbon atoms, and X is a cation selected from the class consisting of hydrogen, sodium, potassium, calcium, lithium, magnesium and ammonium ions.

2. The bath as claimed in claim 1 in which the ,S-alanine is present in an amount between 0.04 and 0209 g./l.

3. The bath as claimed in claim 2 wherein the R radical has from 12 to 14 carbon atoms, the R group is hydrogen, and the cation is the sodium ion.

4. The bath as claimed in claim 2 wherein the R radical has from 12 to 14 carbon atoms, the R group is hydrogen, and the cation is the potassium ion.

70 5. The bath as claimed in claim 2 in whichthe [it-alanine is sodium N-coco S-amino propionate.

6'. The bath as claimed in claim 2. in which the [3-alam'ne is sodium N-lauryl B-amino propionate.

7. The bath as claimed in claim 2 in which the ,B-alanine is triethanol ammonium N-lauryl ,B-amino propionate.

8. The bath as claimed in claim 2 in which the B-alanine is sodium N-lauryl fi-amino butyrate.

9. In a method of electrodepositing a metal selected from the class consisting of copper and copper base alloys, the step of depositing said metal from an alkaline-cyanide bath comprising copper cyanide, free cyanide, and between 0.01 g./l. and 0.2 g./l. of at least one fl-alanine selected from the class consisting of compounds having the following formulae:

wherein R is an alkyl radical having from 8 to 16 carbon atoms in the chain, R is a group selected from the class consisting of hydrogen and alkyl radicals having 1 to 4 carbon atoms, and X is a cation selected from the class consisting of hydrogen, sodium, potassium, calcium, lithium, magnesium and ammonium ions.

10. A method as claimed in claim 9 in which the fi-alanine is present in an amount between 0.04 and 0.09 g./l.

11. A method as claimed in claim 10 in which the ,B-alanine has the general formula the R radical has from 12 to 14 carbon atoms, R is hydrogen, and the cation is the sodium ion.

6 12. A method as claimed in claim 10 in which the B-alanine has the general formula the R radical has from 12 to 14 carbon atoms, R is hydrogen, and the cation is the potassium ion.

13. A method as claimed in claim 9 in which the fi-alanine is sodium N-coco fi-amino propionate.

14. A method as claimed in clam 9 in which the [St-alanine is sodium N-lauryl (i-amino propionate.

15. A method as claimed in claim 9 in which the ,B-alanine is triethanol ammonium N-lauryl ,B-amino propionate.

16. A method as claimed in claim 9 in which the fi-alanine is sodium N-lauryl fi-amino butyrate.

17. In an alkaline cyanide copper electroplating bath, the improvement which comprises the addition of a compound of the formula RNH(CH ),,COOX wherein R is an alkyl radical having from 8 to 16 carbon atoms, n is from 2 to 3, and X is a cation selected from the class consisting of hydrogen and sodium, the amount of said compound being at least 0.01 g./1.

References Cited in the file of this patent UNITED STATES PATENTS 2,255,057 Holt Sept. 9, 1941 2,876,178 McCoy Mar. 3, 1959 2,881,122 Foulke et a1 Apr. 7, 1959 

1. AN IMPROVED ALKALINE-CYANIDE BATH FOR PLATING A METAL SELECTED FROM THE CLASS CONSISTING OF COPPER AND COPPER BASE ALLOYS WHICH COMPRISES COPPER CYANIDE, FREE CYANIDE, AND BETWEEN 0.01 G./1. AND 0.2 G./1. OF AT LEAST ONE B-ALANINE SELECTED FROM THE CLASS CONSISTING OF COMPOUNDS HAVING THE FOLLOWING FORMULAE: 